2. THE NEUROHYPOPHYSIS
155
axons have been seen to terminate against blood vessels, presumably
against those which form a plexus around the neural processes of the
pars nervosa (Green, 1951; Sathyanesan and Chavin, 1967). It appears
that neurosecretory materials could be liberated into these capillaries,
and perhaps reach the general circulation; the presence of a pituitary
portal system suggests that they might also reach the adenohypophysis.
The holostean neurohypophysis is typical of the preteleost bony fish
in most of its characteristics. It is strikingly different from the teleost in
its possession of a pituitary portal system. However, in a few points, such
as the particularly clear division of magnocellular and parvocellular
regions in the preoptic nucleus of Amia culuu, there are hints of the
evolution of the teleosts.
B. The Nature of the Neurohypophysial Principles of the Holostei
Pharmacological and chromatographic evidence suggests that the
holosteans contain the same neurohypophysial principles as those of the
teleost fish. Follett and Heller (1964a) have used paper chromatography
to resolve extracts from the pituitaries of Lepidostew plutostomus and
Amia culva into two active componants. The slow-running principle had
oxytocic, rat vasopressor, avian vasodepressor, and milk-ejection activities
which were compatible with arginine vasotocin. The fast-running moiety
gave oxytocic, avian depressor and milk-ejection effects which were
quantitatively similar to 4 Ser, 8 Ile oxytocin. W. H. Sawyer (1966a,
196Sa) investigated the peptides of the pituitaries of Lepidosteuci osseuci
by both paper chromatography and column chromatography on carboxymethyl cellulose. He separated a principle with high frog bladder activity,
apparently arginine vasotocin, from a neutral peptide which could not
be distinguished from 4 Ser, 8 Ile oxytocin. The results of these two
groups of workers confirm one another and suggest that the Holostei
produce arginine vasotocin and 4 Ser, 8 Ile oxytocin. However, chemical
evidence for these identities is still needed.
These results indicate that arginine vasotocin and 4 Ser, 8 Ile oxytocin
were probably established as neurohypophysial peptides at an evolutionary stage before the modem holosteans diverged from the teleostean bony
fish.
C. The Actions of Neurohypophysial Principles in the Holostei
There are no direct studies of the actions of arginine vasotocin or
4 Ser, 8 Ile oxytocin in the holostean bony fish. It can only be suggested
that the histological evidence suggests a possible role in the control of
155
axons have been seen to terminate against blood vessels, presumably
against those which form a plexus around the neural processes of the
pars nervosa (Green, 1951; Sathyanesan and Chavin, 1967). It appears
that neurosecretory materials could be liberated into these capillaries,
and perhaps reach the general circulation; the presence of a pituitary
portal system suggests that they might also reach the adenohypophysis.
The holostean neurohypophysis is typical of the preteleost bony fish
in most of its characteristics. It is strikingly different from the teleost in
its possession of a pituitary portal system. However, in a few points, such
as the particularly clear division of magnocellular and parvocellular
regions in the preoptic nucleus of Amia culuu, there are hints of the
evolution of the teleosts.
B. The Nature of the Neurohypophysial Principles of the Holostei
Pharmacological and chromatographic evidence suggests that the
holosteans contain the same neurohypophysial principles as those of the
teleost fish. Follett and Heller (1964a) have used paper chromatography
to resolve extracts from the pituitaries of Lepidostew plutostomus and
Amia culva into two active componants. The slow-running principle had
oxytocic, rat vasopressor, avian vasodepressor, and milk-ejection activities
which were compatible with arginine vasotocin. The fast-running moiety
gave oxytocic, avian depressor and milk-ejection effects which were
quantitatively similar to 4 Ser, 8 Ile oxytocin. W. H. Sawyer (1966a,
196Sa) investigated the peptides of the pituitaries of Lepidosteuci osseuci
by both paper chromatography and column chromatography on carboxymethyl cellulose. He separated a principle with high frog bladder activity,
apparently arginine vasotocin, from a neutral peptide which could not
be distinguished from 4 Ser, 8 Ile oxytocin. The results of these two
groups of workers confirm one another and suggest that the Holostei
produce arginine vasotocin and 4 Ser, 8 Ile oxytocin. However, chemical
evidence for these identities is still needed.
These results indicate that arginine vasotocin and 4 Ser, 8 Ile oxytocin
were probably established as neurohypophysial peptides at an evolutionary stage before the modem holosteans diverged from the teleostean bony
fish.
C. The Actions of Neurohypophysial Principles in the Holostei
There are no direct studies of the actions of arginine vasotocin or
4 Ser, 8 Ile oxytocin in the holostean bony fish. It can only be suggested
that the histological evidence suggests a possible role in the control of